Field of the Invention
The present invention relates to a reactive power compensation device (Static Var Compensator: SVC) adjusting a system voltage by supplying reactive power to a power system, and a reactive power compensation system including a plurality of reactive power compensation devices.
Description of the Background Art
A conventional reactive power compensation device slightly changes reactive power to be injected into a power system, and calculates a system impedance, based on the relationship between a change amount of a system voltage and a change amount of the reactive power on that occasion. The reactive power compensation device adjusts one or more control parameters of control means controlling an output amount of the reactive power, using the calculated system impedance. As a result, optimal reactive power compensation can be performed (see, for example, Japanese Patent Laying-Open No. 2007-267440 and Japanese Patent Laying-Open No. 62-203520).
In the conventional reactive power compensation device, since the system impedance is calculated based on the change amount of the system voltage produced when the reactive power to be injected into the power system is changed as described above, the system impedance cannot be determined correctly when the system voltage is changed due to a factor other than injection of the reactive power. For example, the system voltage is changed when a phase-modifying capacitor or a shunt reactor is closed or opened or large-sized load equipment such as a motor is activated or stopped in the vicinity of the reactive power compensation device. When the system voltage is changed due to such an external factor while an injection amount of the reactive power is slightly changed, accuracy in detecting the system impedance is deteriorated, and as a result, the system voltage cannot be controlled appropriately.